Spring Boot 2.x:SpringBoot

Posted benming

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几个重要的事件回调机制:

 

1、配置在META-INF/spring.factories

 

ApplicationContextInitializer

 

SpringApplicationRunlistener

 

2、需要放在ioc容器中

 

     3ApplicationRunner

 

     4CommandLineRunner

 

一、创建SpringApplication对象

 

快速创建一个工程,在SpringBootApplication类中,main方法作为一个入口类,在在run()方法处打上断点,debug运行;

public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {

    //保存主配置类    

this.resourceLoader = resourceLoader;

    Assert.notNull(primarySources, "PrimarySources must not be null");

    this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));

    //判断当前是否一个web应用

    this.webApplicationType = WebApplicationType.deduceFromClasspath();

    //从类路径系找到META-INF/spring.factories配置的所有ApplicationContextInitializer,然后保存起来

    setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));

    //从类路径系找到META-INF/spring.factories配置的所有ApplicationListener

    setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));

    //从多个配置类中找到有main方法的主配置类

    this.mainApplicationClass = deduceMainApplicationClass();

}

二、运行run方法

 

接着上一步的继续进行:

public ConfigurableApplicationContext run(String... args) {

    StopWatch stopWatch = new StopWatch();

    stopWatch.start();

    ConfigurableApplicationContext context = null;

    Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();

    configureHeadlessProperty();

    //获取SpringApplicationRunListeners ,从类路径下METTA-INF/spring.factories

    SpringApplicationRunListeners listeners = getRunListeners(args);

    //回调所有的SpringApplicationRunListeners.starting方法

    listeners.starting();

    try {

        //封装命令行参数

        ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);

        //准备环境

ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);

        //创建环境完成后回调SpringApplicationRunListeners.environmentPrepared();表示环境准备完成

configureIgnoreBeanInfo(environment);

Banner printedBanner = printBanner(environment);

        //创建applicationContext,决定创建webioc还是普通的ioc

context = createApplicationContext();

exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,

new Class[] { ConfigurableApplicationContext.class }, context);

        //准备上下文环境;将environment保存到ioc中;而且applyInitializers()

        //applyInitializers():回调之前保存的所有的ApplicationContextInitializerInitialize方法

        //回调所有的SpringApplicationRunListeners.contextPrepared()

prepareContext(context, environment, listeners, applicationArguments, printedBanner);

        //prepareContext运行完成以后回调所有的SpringApplicationRunListenerscontextLoaded()

        //刷新容器;ioc容器初始化(如果是web应用还会创建嵌入式的tomcat);spring注解

        //扫描,创建,加载所有组件的地方;(配置类,组件,自动配置)

refreshContext(context);

        //ioc容器中获取所有的ApplicationRunnerCommandLineRunner进行回调

        //ApplicationRunner先回调,CommandLineRunner再回调

 

afterRefresh(context, applicationArguments);

stopWatch.stop();

if (this.logStartupInfo) {

    new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);

}

        listeners.started(context);

callRunners(context, applicationArguments);

    }

    catch (Throwable ex) {

handleRunFailure(context, ex, exceptionReporters, listeners);

throw new IllegalStateException(ex);

    }

 

    try {

        listeners.running(context);

    }

    catch (Throwable ex) {

        handleRunFailure(context, ex, exceptionReporters, null);

        throw new IllegalStateException(ex);

    }

    //整个SpringBoot应用启动完成外汇返佣以后返回启动的ioc容器

    return context;

}三、事件监听机制

依次将上面的几个监听机制进行创建,

HelloApplicationContextInitializer

public class HelloApplicationContextInitializer implements ApplicationContextInitializer<ConfigurableApplicationContext> {

    @Override

    public void initialize(ConfigurableApplicationContext applicationContext) {

        System.out.println("ApplicationContextInitializer...initialize..." + applicationContext);

    }

}

HelloSpringApplicationRunListener

public class HelloSpringApplicationRunListener implements SpringApplicationRunListener {

    

    public HelloSpringApplicationRunListener(SpringApplication application, String[] args){

 

    }

 

    @Override

    public void starting() {

        System.out.println("SpringApplicationRunListener...starting...");

    }

 

    @Override

    public void environmentPrepared(ConfigurableEnvironment environment) {

        Object o = environment.getSystemProperties().get("os.name");

        System.out.println("SpringApplicationRunListener...environment" +o);

    }

 

    @Override

    public void contextPrepared(ConfigurableApplicationContext context) {

        System.out.println("SpringApplicationRunListener...contextPrepared");

    }

 

    @Override

    public void contextLoaded(ConfigurableApplicationContext context) {

        System.out.println("SpringApplicationRunListener...contextLoaded");

    }

 

    @Override

    public void started(ConfigurableApplicationContext context) {

        System.out.println("SpringApplicationRunListener...started");

    }

 

    @Override

    public void running(ConfigurableApplicationContext context) {

        System.out.println("SpringApplicationRunListener...running");

    }

 

    @Override

    public void failed(ConfigurableApplicationContext context, Throwable exception) {

        System.out.println("SpringApplicationRunListener...failed");

    }

    

 

}

HelloApplicationRunner

@Component

public class HelloAppicationRunner implements ApplicationRunner {

    @Override

    public void run(ApplicationArguments args) throws Exception {

        System.out.println("ApplicationRunner...run..");

    }

}

HelloCommandLineRuinner

@Component

public class HelloCommandLineRunner implements CommandLineRunner{

 

    @Override

    public void run(String... args) throws Exception {

        System.out.println("CommandLineRunner...run..." + Arrays.asList());

    }

}

前面提到的ApplicationContextInitializerSpringApplicationRunlistener是需要进行配置的,配置的位置是在META-INF/spring.factories中,因此创建一个META-INF的文件夹,并创建spring.factories文件,

org.springframework.context.ApplicationContextInitializer=

com.itlaoqi.springbootspringbootapplication.listener.HelloApplicationContextInitializer

 

org.springframework.context.SpringApplicationRunListener=

com.itlaoqi.springbootspringbootapplication.listener.HelloSpringApplicationRunListener

配置完成后启动项目即可进行测试。

原文链接:https://blog.csdn.net/cyl101816/article/details/103582373

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